1, 4-bis-(3-aminopropoxy)-cyclohexane



Patented Dec. 4, 1 951 1,4-BIS- (3-AMINOPROPOXY) -CYCLOHEXANE Geoffrey Bilson May and James Wotherspoon Fisher, Spondon, near Derby, England, assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application August 3, 1948, Serial No. 42,350. In Great Britain August 22, 1947 According to the invention compounds containing a l:e-bis-ethoxy-cyclohexane residue are made by a process which includes the step of causing acrylonitrile to react with quinitol in a reaction mixture containing the acrylonitrile and quinitol in a molecular ratio of 2:1 or higher and in the presence of a basic substance as a catalyst. The primary product of the reaction is 1 I-bis- (z cyanoethoxy) -cyclohexane, and this compound can readily be converted into 1:4-bis- (3'-aminopropoxy)-cyclohexane by catalytic hy drogenation and into 1:-bis-(2 carboxyethoxy) cyclohexane or esters thereof by hydrolysis-or alcoholysis.

The reaction of the quinitol and acrylonitrile may be carried out by heating quinitol with acrylonitrile, preferably in solution and preferably inthe presence of a small amount of a substancecapable of inhibiting addition polymerisation of unsaturated compounds, e. g. quinol. We havefound it best to employ a considerable excess of the acrylonitrile, especially 4-12 and more particularly 5-8' molecular proportions for each molecular proportion of quinitol. Advantageously the acrylonitrile and quinitol are dissolved in an alcohol containing an alkali metal alkoxide, and it is preferable to employ only sufiicient alcohol to dissolve the reactants or not much more than that amount. Thus a concentrated solution of the quinitol and acrylonitrile, together with a trace of quinol' as polymerisation inhibitor, in ethyl alcohol to which a little sodium has been added, may be boiled under reflux for a few hours, e; g. for 1-3 hours. If the solution is then filtered and cooled, l:4-bis(2-cyanoethoxy)-cyclohexaneseparates out and can be filtered, offand, if desired, recrystallized from hot water. Unchanged acrylonitrile and quinitol can be recovered from the filtrate, for example by first distilling oiT the acrylonitrile under atmospheric pressure and then distilling the bulk of the residue under reduced pressure and cooling this second distillate to cause the quinitol to separate out.

The hydrogenation of the bis-cyanoethoxycyclohexane to 1 l-bis- (3-aminopropoxy) -cyclohexane can be carried out by heating a solution of the bis-cyanoethoxy-cyclohexane with a hydrogenation catalyst under a suitable hydrogen pressure,- preferably in the presence also, of ammonia. Examples of suitable solvents are methanol and dioxane. Nickel hydrogenation catalysts have been found to be effective, especialy a catalyst comprising nickel deposited on kieselguhr or Raney nickel. With nickel catalysts of these types the hydrogenation may be carried out at'a temperature between about 50 C. or 100 C. and 150 C. under a hydrogen pressure of 50-300 atmospheres. When the hydrogenation is complete, the catalyst may be filtered oil or otherwise separated from the products of the hydrogenation, and the bis-aminopropoxycyclohexane isolated by evaporating ofi the solvent.

The hydrolysis of the 1 :4-bis-(2-cyanoethoxy) cyclohexane to the corresponding dicarboxylic acid is preferablyperformed by warming the biscyanoethoxy-cyclohexane with an acid, especially with a fairly concentrated aqueous hydrochloric acid solution. We have found it important that the conditions of the hydrolysis should be mild, and that it is advisable not to heat the mixture of the bis-cyanoethoxy-cyclohexane and the hydrochloric acid to a temperature substantially exceeding about C. or C. Advantageously the mixture may be kept at about 50 C. for a fairly long time, e. g. for 1-7 days and especially for about 2 days. The hydrochloric acid may be employed in considerable excess, for example in 3-5 times excess (i. e. 6-10 molecular proportions of hydrogen chloride for each molecular proportion of the bis-cyanoethoxy-cyclohexane). The bis-carboxyethoxycyclohexane produced may be isolated by evaporating the solution resulting from the hydrolysis, drying the residue and recrystallizing from benzene.

To produce a dicarboxylic ester instead of the dicarboxylic acid, the bis-cyanoethoxy-cyclohexane may be subjected to alcoholysis. In this reaction also it is preferable to employ an acid, especially hydrochloric acid, as catalyst, but the reaction. can be carried out at higher temperatures than are advisable for the hydrolysis to the free dicarboxylic acid. For example the di ethyl ester may be made by boiling the hiscyanoethoxycyclohexane under reflux with an excess of ethyl alcohol and with water, preferably in amount equal to or somewhat less than that theoretically required, while passing hydrogen chloride gas through the solution. Ammonium chloride separates out and at the end of the reaction the solution may be filtered and excess alcohol removed from the filtrate by distillation. If the residue is cooled and. diluted. with Water, it separates into two layers, the lower of which contains the desired diethyl ester.

which may be isolated by extraction with ether. Other diesters, e. g. the di-isopropyl ester, can be made by employing the appropriate alcohol in place of ethyl alcohol.

Esters of 1:4-bis -(2-carboxyethoxy)-cyclohexane can also be made by esterifying the free acid, for example by heating it with the desired alcohol in the presence of an esterification catalyst. Thus the diethyl ester may be made by boiling under reflux a solution of the free biscarboxyethoxy-cyclohexane in ethyl alcohol, pref erably in considerable excess, to which some sulphuric acid has been added or through which hydrogen chloride is passed during the reaction. Other methods of esterification may be employed; for example the bis-carboxyethoxy-cyclohexane may be converted into its dimethyl ester by means of dimethyl sulphate.

Cyclohexane and its derivatives exist in two geometrically isomeric forms known respectively as the cis and trans. forms, the latter being the more stable. When quinitol is produced by the catalytic hydrogenation of quinol, a mixture of the cis and trans forms is obtained, and it is possible, by heating this mixture, to obtain a product which is substantially wholly the trans form; if the cis form is required, it may be separated from admixture with the trans form by making use of the different solubilities of the two forms in acetone. The reactions described in this present specification take place with both the cis and trans forms and also with mixtures of the two forms of quinitol and the alkoxy-cyclohexane derivatives made from it.

Among the novel ethers with which the invention is concerned, 1:4-bis-(3-aminopropoxy)- cyclohexane is of special interest as an intermediate in the manufacture of polymeric substances, including high linear polymers. Thus a mixture of 1:4-bis-(3-aminopropoxy) -cyclo hexane and a dibasic carboxylic acid, especially a dicarboxylic acid, or an amide-forming derivative of a dibasic carboxylic acid, or a salt of the bis-aminopropoxy-cyclohexane and the dibasic acid, may be heated until a polyamide has been formed. Examples of dicarboxylic acids which will produce polyamides by reaction with the bisaminopropoxy-cyclohexane are adipic acid, sebacic acid and other straight chain aliphatic dicarboxylic acids having the carboxyl groups in the terminal positions, terephthalic acid, bis-(pcarboxyphenoxy) -alkanes, e. g. 1:2-bis-(p-carboxyphenoxy) ethane, 1:6 bis (p-carboxyphenoxy)-hexane and the corresponding thioether acids, 2:2'bis(p-carboxyphenoxy) -diethyl ether and similar derivatives of other dialkyl ethers and of dialkyl thio-ethers, hydroquinone diacetic acid (1 :4-bis-(carboxymethoxy) -benzene), hydroquinone di-p-benzoic acid (1:4-bis- (p-carboxyphenoxy) -benzene) bis-(p-carboxyphenyD-methane and bis-(p-carboxyphenyl) derivatives of other alkanes, p:p'-dicarboxydiphenyl naphthalene-1:5, 2:6- and 2:7-dicarboxylic acids, 1:4 bis (p carboxyphenoxymethyl) -benzene, and p:p'-dicarboxydiphenylether and the corresponding thio-ether. Short chain dicarboxylic acids, i. e. acids containing fewer than 6 carbon atoms such as oxalic acid, and also carbonic acid, can be used (preferably in the form of their esters), especially if fibre-form- In the production of the polyamides it is preferred to heat the basic and acidic reactants or a salt formed therefrom to a temperature above 200 C. and especially above 220 C., advantageously in the practical absence of oxygen, e. g. in a hydrogen or nitrogen atmosphere. The polymerisation may be effected in a single continuous operation or in two or more operations; for example a polymer of relatively low molecular weight may first be formed, and if it is desired to produce a polymer of high molecular weight, for instance a polymer having fibre-forming properties. the relatively low polymer can be further heated until it has acquired the desired Qualities. In the early stages of the polymerisation, the reactants or a salt formed therefrom may be heated under substantially atmospheric pressure or under a pressure higher than atmospheric produced, for example, by working under constant volume conditions in a pressure vessel; usually, however, in order to produce a product capable of being formed into useful fibres, it is advisable in the final stages to reduce the pressure to below 5 mm. and preferably to about 2 mm. or lower.

ing properties are not desired. On being subjected to hydrolysis all these polymers yield 1:4- bis-(3-aminopropoxy) -cyclohexane (in the form of a salt with the hydrolysing acid) and the free dibasic carboxylic acid.

In order to produce polymers of h gh molecular weight the basic and acid reactants should be employed in substantially equimolecular quantitles. (The expression substantially equimolecular quantities is employed to indicate that neither reactant is present in an excess greater than 5% over the other; preferably neither is present in an excess greater than 2%.) If polymers having fibre-forming properties are desired, the acid reactant preferably comprises two carboxyl groups separated by a chain of at least four atoms.

If desired 1:4 bis-(3-aminopropoxy) -cyclohexane can be used in association with other diamines, especially straight chain aliphatic diamines such, for example, as hexamethylene diamine or tetramethylene diamine, in the production of mixed polyamides. Similarly mixtures of more than one dibasic acid can be used if desired, for instance mixtures of two or more of the dicarboxylic acids mentioned above.

High linear polymers made in accordance with the invention may be used in the manufacture of filaments, yarns and other shaped products by melt-spinning methods and also in moulding compositions and the like.

It is also possible to use the novel ethers, especially 1:4 bis (3 aminopropoxy) -cyclohexane, in the production of insoluble and infusible resins by causing them to react with compounds containing 3 or more reactive groups so that cross-linking can occur.

Either the cis or trans forms or mixtures of the cis .and trans forms of the ethers can be used in the production of polymers.

The invention is illustrated by the following examples; the parts specified are in all cases parts by weight.

Example 1 273 parts of quinitol, 752 parts of acrylonitrile and 9.4 parts of quinol were added to ethyl alcohol to which a little sodium had been added so as to form sodium ethoxide, and the mixture was boiled under reflux conditions for 1 hours. A green black solution was obtained which, while still hot, was filtered. On cooling the solution, a brown solid separated out; this was filtered off and washed with cold water until it was nearly White and was then recrystallized from hot water. The product was 1:4-bis-(2-cyanopassing into it dry hydrogen chloride,

98 parts of 1:4-bis(2-cyanoethoxy)-cyclohexane prepared in accordance with Example 1 was added to 464 parts of 32% ,aqueoushydrochloric acid, and the mixture was stirred at .room temperature forj2a hours, after which the temperature was slowly raised to 50 C. with continued stirring for a further '28 hours. After being cooled, the resulting mixture was filteredand the solid residue was extracted several times with ether and chloroform. On evaporating the extracts, 1:d bis-(Z-carboxyethoxy) .cyclohexane was obtained asa white crystalline solid. The filtrate was evaporated to dryness under vacuum and the residue was extracted with ether and chloroform, giving a further quantity of the bis-carboxyethoxy cyclohexane. 1:4 bis (2- carboxyethoxy)--cyclohexane has M. P. 110 C. and is soluble in water, acetone, chloroform, ether, alcohol and hotbenzene.

Example 3 50 parts of lz l-bis-(Z-cyanoethoxy) -cyclohexane produced in accordance with Example 1 was added to 215 parts of 95% ethyl alcohol and the mixture was boiled under reflux for 4 hours while Ammonium chloride separated out as the reaction proceeded. The product was cooled and filtered and alcohol removed from the filtrate by distillation. The residue from the distillation was cooled'gand diluted with water, whereupon .it' separated into two layers. The lower layer was extracted with ether; the extract Was washed with a little so dium bicarbonate solution and driedover sodium sulphate, after which the ether was distilled off under atmospheric pressure and the residue was distilled under a pressure of 15 mm., the diethyl ester of 1 l-bis- (Z-carboxyethoxy) cyc1ohexane coming over between 200 C. and 205 C.

Example 4 46 parts of 1:4-bis-(2-cyanoethoxy) -cyclohexane was introduced into an autoclave together with 63 parts of methanol, 32 parts of liquid ammonia and a catalyst consisting of nickel deposited on kieselguhr. Hydrogen was admitted under a pressure of 240 atmospheres and the autoclave heated to 130 C.-140 C. for about 1 hour. After being cooled the products were freed from the catalyst by filtration and the methanol was distilled off under atmospheric pressure. The residue was distilled under a pressure of 30 1pm., and the crude 1:4-bis-(3-aminopropoxy)-cyclohexane so obtained was purified by fractional distillation, again under 30 mm. pressure, the fraction coming over at 205-212 C. under this pressure being collected.

Example 5 11.5 parts of 1:4-bis-(3-aminopropoxy) -cyclohexane and 7.3 parts of adipic acid were dissolved in separate portions of methanol and the solutions mixed. A very dilute solution of the diamine in methanol Was then added cautiously until the mixture was feebly alkaline to litmus. Ether was then added until the adipate of the diamine precipitated as a white solid of M. P. 176 C.

This salt was heated under nitrogen for 2 hours at 200 C., and then at 220 C. for a further hour under a pressure of 2 mm. The prodnot wasa'light-coloured, hard polymeruof M. P. 196 C. which could be formed into fibres capable of lbeing cold drawn and insoluble in water and acetone.

Example 6 1.3 parts of diethyl oxalate was dissolved .in .4 parts of methanol and added very gradually to a solution .of 11.5 parts of 114-bis-(3-aminopropoxy)-:cyclohexane .in 4 parts of methanol. A considerable amount of heat was evolved and a heavy white solid precipitated. The mixture was well stirred and allowed to cool and the white solid filtered olf. This White solid was a low polymer of'M. P. 251 C., insoluble in water and methanol. "I-o obtain a high polymer the solid was heated under nitrogen at 260 C. until it had melted, whereupon the pressure was reduced to '2 mm. and heating continued at about the same temperature for '2 hours. The polymer produced had M. P. 246 C.

A similar product was obtained by heating a mixture of equal parts of the low polymer and m-cresol for 3 hours at 210-22-0 C. under nitrogen, dissolving the product in formic acid and precipitating the polymer with water.

Example 7 4.6 parts of 1:4bis-(3-aminopropoxy) -cyclohexane was dissolved in methanol and the solution added to 33 parts of terephthalic acid and sufiicient water to give an aqueous methanol, and the solution was boiled under reflux until it became clear. It was then diluted with methanol and allowed to cool, whereupon the terephthalate of the diamine gradually crystallized out as a white, water-soluble solid of M. P. 262 C.

Equala-mounts of. this salt and of m-cresolwere heated under nitrogen at 220 C. for about 1 1 hours, after which the resultant polymer had separated as a light-coloured, hard mass of 'M. P. 284 C., insoluble in water and acetone and yielding fibres capable of being cold drawn.

Example 8 4.6 parts of 1:4-bis-(3-aminopropoxy)-cyclohexane was dissolved in 80% aqueous methanol and boiled under reflux with 6.04 parts of 1:2- bis(p-carboxyphenoxy) -ethane until a clear solution was obtained. The solution was then diluted with methanol, whereupon the diamine salt of the dicarboxylic acid precipitated as a white crystalline solid of M. P. 239-240 0.

Equal weights of this salt and of m-cresol were heated under nitrogen for 1 hour at 210-220 C., after which the solution was allowed to cool, whereupon it set to a light-coloured, hard mass. This was dissolved in cold formic acid and the solution so obtained was poured into water to precipitate the polymer as a powder of M. P. 250 C. which could be formed into fibres capable of being cold drawn.

Alternatively, the salt was heated in the absence of a solvent under nitrogen to 260 C. for 20 minutes and then for a further hour at the same temperature but under a pressure of 2 mm. The properties of the polymer so obtained were similar to those of the polymer obtained by carrying out the polymerisation in the presence of m-cresol.

Example 9 2.3 parts of 1:4-bis-(3-aminopropoxy)-cyclohexane was dissolved in 80% aqueous methanol and boiled under reflux with 3.3 parts of 1:4-bis- (p-carboxyphenoxy)-butane until a clear soluwhereupon the salt of the diamine and dicarboxylic acid slowly crystallized as a white powder of M. P. 200 C. The salt was heated under nitrogen :at 240 C. for 4 hours and then under'a pressure of2 mm. at 240 C. for 1 hour and at 260-270 C. for a further hour.

The product was a lightcoloured polymer of M. P. 224 C. capable of being formed into fibres.

Example 10 2.3 parts of lz4-bis-(3-aminopropoxy)-cyclohexane was dissolved in 80% aqueous methanol and the solution boiled under reflux with 3.58 parts of 1 6-bis- (p-earboxyphenoxy) -cyclohexane until a clear solution was obtained, parts of water being added after 10 minutes to aid solution. The resulting solution was diluted with methanol and cooled, whereupon the salt slowly crystallized as a white powder of M. P. 203-204 C. The salt was heated under nitrogen for A; hour at 240 C. and then for 1 hour at the same temperature but under a pressure of 2 mm. The polymer obtained had M. P. 210-215 C. and gave fibres capable of being cold drawn.

Example 11 2.3 parts of 1:4-bis-(3-aminopropoxy)-cyclohexane was dissolved in 80% aqueous methanol and boiled under reflux with 3.46 parts of 2:2-

bis-(p-carboxyphenoxy)-diethyl ether until a clear solution was obtained. The solution was concentrated and dioxane added to precipitate the 2.7 parts of 1:4-bis-(3-amlnopropoxy)-cyclohexane was dissolved in aqueous methanol and an equal weight of hydroquinone diacetic acid added. The solution was then diluted with methanol, in order to cause the salt so formed to separate as a soft crystalline solid of M. P. 202 C. The salt when heated for /2 hours at 240 C. under nitrogen gave a polymer of M. P. -160 C. which could be formed into fibres capable of being cold drawn.

Having described our invention, what we desire to secure by Letters Patent is:

As a new substance, 1:4-bis-(3-aminopropoxy) -cyclohexane.

GEOFFREY BILSON MAY. JAMES WOTHERSPOON FISHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,782,729 Klingemann et a1. Nov. 25, 1930 2,130,523 Carothers Sept. 20, 1938 2,329,432 Bruson Sept. 14, 1943 2,383,443 Bruson Aug. 28, 1945 2,401,607 Bruson June 4, 1946 2,437,905 Bruson Mar. 16, 1948 FOREIGN PATENTS Number Country Date 796,001 France Mar. 27, 1936 870,544 France Mar. 13, 1942 OTHER REFERENCES Olberg et al., Am. Chem. Soc, vol. 66, pp. 1096-1097 (1944). 

